Bonn 2001 – scientific programme

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T: Teilchenphysik

T 304: Feldtheorie 2

T 304.7: Talk

Tuesday, March 27, 2001, 17:45–18:00, HS III

Polarized quark and antiquark distribution functions in the chiral quark soliton model — •P. Schweitzer¹, B. Dressler¹, K. Goeke¹, P.V. Pobylitsa^1,2, M.V. Polyakov^1,2, M. Strikman³, D. Urbano⁴, and C. Weiss¹ — ¹Institut für Theoretische Physik II, Ruhr–Universität Bochum, D–44780 Bochum, Germany — ²Petersburg Nuclear Physics Institute, Gatchina, St. Petersburg 188350, Russia — ³Pennsylvania State University, University Park, PA 16802, USA — ⁴Faculdade de Engenharia da Universidade do Porto, 4000 Porto, Portugal

The chiral quark-soliton model (χQSM) is an effective relativistic low energy theory derived from the instanton model of QCD vacuum. It describes the nucleon as a chiral soliton of the pion field in large N_c-limit. Nucleonic observables can be computed without adjustable parameters. In particular it yields a consistent description of twist two quark and antiquark parton distributions of the nucleon at a low normalization point of 600 MeV. Bjorken sum rule, Soffer inequalities, positivity requirements, etc. are fulfilled. The model results for the unpolarized quark and antiquark distributions and the helicity quark distributions agree well with parameterizations. In the case of helicity antiquark distributions the model predicts a large flavour asymmetry. The large flavour asymmetry is consistent with present SIDIS data and strongly affects the predictions for spin asymmetries measurable in the Drell-Yan process with polarized nucleons. The transversity distribution is predicted to be significantly different from the helicity distribution already at a low scale. Both distributions can be related by simple parameterizations.